The present invention relates to flame holders, particularly for gas turbine combustors.
As is known, aerodynamic stabilization of the flame is necessary in most gas turbine combustors, as well as in jet engines, afterburners, and rocket engines, because the bulk velocity of the gaseous flow generally exceeds the turbulent flame speed. Without stabilization, a flame would otherwise blow downstream and be extinguished. In addition, mixing of the various gaseous components present in a combustor is generally effected by the turbulence associated with a flame holder. Such mixing is quite beneficial, and desirably should be enhanced for the reason that it improves the characteristics of the combustion reaction to limit pollutant emissions. Of particular concern has been the emissions of nitrogen oxides (NO.sub.x), because such oxides are a precursor to air pollution. It is known that NO.sub.x formation increases with increasing flame temperature and with increasing residence time.
Flame stabilization is usually accomplished by employing devices such as swirlers, various kinds of bluff body flame holders, or by air jets. For example, an air swirler for a gas turbine combustor is disclosed in commonly-assigned Hopkins U.S. Pat. No. 3,630,024 and in commonly-assigned Hill et al U.S. Pat. No. 3,608,309.
One common device for stabilizing a flame, particularly in jet engine afterburners or augmentors is a "V-gutter". For example, V-gutter flameholders for afterburners are disclosed in the commonly-assigned Nerad et al U.S. Pat. No. 2,948,117, in the commonly-assigned Vdoviak U.S. Pat. No. 3,931,707, and in the commonly-assigned Nash U.S. Pat. No. 4,064,691, as well as in the Ernst U.S. Pat. No. 4,185,458. A typical V-gutter comprises a pair of elongated walls joined at a lineal vertex and diverging to respective trailing edges. The V-gutter extends across a main flow stream of gaseous components, and is oriented with the vertex pointed upstream. Flow across the V-gutter causes a recirculation region (wake) downstream of the V-gutter. The Nerad et al patent discloses a modified annular V-gutter flameholder having vortex generators mounted at spaced locations along the length of the modified V-gutter. The flameholders of the Voviak and Nash patents include both annular and radially-extending V-gutter flame holders within the same afterburner.
By way of further example, other forms of stabilization devices or swirlers are disclosed in the Lefebvre et al U.S. Pat. No. 4,134,260 and Egan, Jr. et al U.S. Pat. No. 4,170,109.